Measurements of superconducting phase gradients by a nanowire quantum interference device templated by DNA molecules

Abstract

Previously employed wet-chemistry approaches to DNA metallization from granular wires that become highly resistive at low temperatures. We have developed a process to make superconducting nanowires templated by DNA molecules that are homogeneous, are less than 10 nm in diameter, make seamless contacts the leads, and become superconducting at low temperatures. Our method involves isolating single DNA strands stretched across a narrow but deep trench and sputter-coating MoGe on the DNA scaffold. We have used these nanowires as the basis for a quantum interference device in which two wires are connected in parallel by superconducting films. We have discovered resistance oscillations for the two-wire device as a function of phase gradients in the leads caused by magnetic screening currents or applied currents, and we have developed a theory to explain our observations based on an extension of the Langer- Ambegaokar-McCumber-Halperin theory of thermally activated phase slips. In addition, we also measure the effect of vortex motions on these oscillations and confirm the field dependence of the Campbell penetration depth.